The KNX system offers the choice for the manufacturers, depending on his market requirements and habits, to choose between several physical layers, or to combine them. With the availability of routers, and combined with the powerful interworking, multi-media, and also multi-vendor configurations can be built.
The different media are :
• TPo, inherited from BatiBUS, and TP1, basic medium of EIB, provide both improved solutions for twisted pair cabling, both using a SELV network and supply system. Main characteristics are : data and power transmission with one pair (devices with limited power consumption may be powered by the bus), and asynchronous character oriented data transfer and half duplex bi-directional communication. TP0 transmission rate is 4.8kbits/s while TP1 is 9.6 kbits/s. Both media implement a CSMA/CA collision avoidance. All topologies may be used and mixed ( line, star, tree, ….)
• PL 110, from EIB, and PL 132 from EHS, enable communication over the mains supply network. Main characteristics are :
• Spread frequency shift keying signalling,
• Asynchronous transmission of data packets
• Half duplex bi-directional communication.
Both differ mainly by their central frequency; 110 and 132 kHz, their decoding process, and data rate; PL110=1200 bits/sec; PL132 = 2400 bits/sec. Both media implement CSMA and are compliant to EN 50065-1, respectively in frequency band without and with standard access medium protocol.
• RF, and IR will soon be specified to communicate in the same way over radio-frequency, or Infra-red media.
• Beyond these Device Network media, KNX has unified service- and integration solutions for IP-enabled media like Ethernet (IEEE 802.2), Bluetooth, WiFi /Wireless LAN (IEEE 802.11), “FireWire” (IEEE 1394) etc.